If you run out of gain, it is a big deal. The 350's have to be pretty much maxed out to achieve the same SPL. It is pretty much impossible to calibrate to 75dB's with the 600 in the loop.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85